The update introduces a wealth of new features into the popular web browser, notably a Do Not Track option which allows users to opt out of online behavioral tracking. There’s also a cleaned-up interface, mirroring the look of Chrome, which Microsoft is also adopting in IE9.

Content management has been improved as well with a variety of added features. Settings, bookmarks, saved passwords, history and open tabs can now be synchronized across multiple devices. Tabs can also be organized using a simple drag-and-drop interface that allows them to be split into nameable groups, with the pages laid out as a series of clickable thumbnails.

The rest of the features aren’t as immediately apparent, but Firefox 4 is outfitted with a number of under the hood updates. It is considerably faster than previous versions, though it remains to be seen how the browser will measure up against Chrome 10 and IE9. There is also improved HTML5 functionality and added support for WebM, an HD video format designed for use with HTML5. Plenty of other features as well, including WebGL support for 3D graphics and hardware acceleration. You can get the full list in Mozilla’s release notes.